The within-subject variability of various pulsatile hormone release characteristics is unknown. Fifteen eumenorrheic women in the early follicular phase of the menstrual cycle will be studied on two occasions separated by a month. Blood samples will be withdrawn at 10 minute intervals for 24 hours for growth hormone and gonadotropin determination. Data will be analyzed by standard pulse detection techniques. The intrasubject reduced data will be compared for test-retest reliability by standard statistical techniques.